1. Field of the Invention
The present invention relates to a linear compressor for compressing refrigerant by using a reciprocating piston. More particularly, the present invention relates to a piston operating assembly for the linear compressor and a method for manufacturing the same.
2. Description of the Prior Art
Generally, a linear compressor compresses a refrigerant by reciprocating a piston with a changing magnetic field. Such a compressor is shown in FIGS. 1 through 3.
As shown in the drawings, the linear compressor includes a cylinder portion 10, a piston 20, a piston operating assembly 30 and an external lamination portion 40, all of which are disposed in a chamber 1.
As shown in FIG. 2, the piston operating assembly 30 includes a magnet holder 32, which is a hollow cylinder having a hole formed in an outer circumference thereof, a magnet 33 inserted in the hole of the magnet holder 32, a magnet cover 35 press fit on the outer circumference of the magnet holder 32 to prevent any accidental separation of the magnet 33 from the magnet holder 32, and a linking member 31 having a hole formed on the center portion thereof for receiving the piston 20. The linking member 31 is connected to one end of the magnet holder 32.
The piston 20 is a hollow cylinder, having one end attached to a suction valve 25 and the other end coupled to the linking member 31 of the piston operating assembly 30. The piston 20 can be secured to the linking member 31 by one of a number of methods, such as welding, etc.
The cylinder portion 10 includes a cylinder 11, in which the piston 20 is received for reciprocating movement, an internal lamination 13 inserted about the outer circumference of the cylinder 11, and a coil 15 wound about the center portion of the internal lamination 13.
An external lamination portion 40 includes an external lamination 41 formed a predetermined distance from the internal lamination 13, a housing 43 for supporting the external lamination 41, and a frame 42.
The operation of the linear compressor constructed as above will be described below.
First, when Alternating Current (AC) voltage is applied to the coil 15 of the internal lamination 13, a magnetic field having N-S poles is generated between the internal and external laminations 13 and 41, respectively. Due to the presence of the permanent magnet 33 disposed between the internal and external laminations 13 and 41, a force in an axial direction is generated according to Flemming""s left-hand rule. As the N-S poles of the magnet 33 are varied, the magnet 33 reciprocates, and accordingly, the piston 20 also reciprocates.
Next, a refrigerant is introduced into the chamber 1 through an inlet tube 3 by the reciprocating movement of the piston 20. The refrigerant flows through the piston 20 and the suction valve 25 and into a compressing chamber 5. When the refrigerant is compressed in the compressing chamber 5, the refrigerant is then discharged through an outlet tube 7.
The conventional linear compressor, however, has several shortcomings. First, some parts of the compressor require forceful coupling methods, such as force fit, welding, etc., to secure the parts together. For example, the piston 20 and linking member 31 are welded together, as are the linking member 31 and the magnet holder 32. Further, the magnet holder 32 must undergo processes like cutting, punching and welding. The force of the couplings and heat distortion of the respective parts produce an internal stress that affects the integrity of the parts. Further, the conventional linear compressor has a complex and lengthy assembly process, while producing a high possibility of defective products. As a result, productivity and throughput are deteriorated.
The manufacturing process of the magnet holder 32 is described in greater detail with reference to FIG. 3. First, a metal plate 32a of a predetermined size is prepared. Then, the metal plate 32a undergoes a rolling process. Next, the ends of the metal plate 32a are welded together to form a hollow cylinder 32b. The hollow cylinder 32b is then punched to form a plurality of holes 32c therein. Finally, in order to prevent any accidental separation of the magnets 33 from the hollow cylinder 32b, a magnet cover 35 is force fit onto the outer circumference of the hollow cylinder 32b. 
In the conventional linear compressor, the different sizes of and deviations among the magnets 33 make it difficult to press fit or force fit the magnet cover 35. When the magnet cover 35 is forcefully press fit, without taking into consideration the different sizes of the magnets 33, those magnets 33 that are more fragile can be broken.
Further, according to a conventional way of assembling the piston operating assembly 30 of the linear compressor, an error in concentricity occurs when the piston 20 and the magnet holder 32 are welded to the linking member 31, and errors in circularity and concentricity occur when press fitting the magnet 33, which is press fit in the magnet holder 32, in the magnet cover 35. Accordingly, productivity and throughput deteriorate. Further, since there are numerous parts that must be assembled together, all of which affect the geometric tolerance of the piston operating assembly 30, the assembly tolerance is increased due to an accumulation of the tolerances of the respective parts. When the geometric tolerance and the assembly tolerance exceed a predetermined degree, the same becomes a defect factor, which can cause problems, such as a malfunction of the linear compressor, etc.
In addition, in the conventional method of assembling the linear compressor, a non-magnetic metal is used to form the magnet holder 32, thereby preventing a leakage of the magnetic force from the magnet 33. The non-magnetic metal of the conventional linear compressor, however, has a relatively higher conductivity, which hinders a complete absence of the magnetic force leakage from the magnet 33. Accordingly, due to the leakage of the magnetic force from the magnet 33, the compression efficiency of the linear compressor is negatively affected.
The present invention has been made to overcome the above-mentioned problems of the prior art. Accordingly, it is an object of the present invention to provide a piston operating assembly for a linear compressor having a piston coupling boss coupled with a piston, a plurality of magnets, and a linking member. The linking member connects the piston coupling boss with the magnets, all of which are integrally secured to the linking member when the linking member is injection molded. Thus, the integrated piston operating assembly has improved geometric and assembling tolerances and no deterioration of persistence.
It is another object of the present invention to provide a method for manufacturing a piston operating assembly for a linear compressor. In the present method the processes are simplified while resulting in a higher productivity.
The above object is accomplished by a piston operating assembly of a linear compressor for compressing a refrigerant with a piston that linearly reciprocates due to a magnetic field. The piston operating assembly includes a piston coupling boss for coupling to the piston, a plurality of magnets disposed in a cylindrical arrangement concentric with respect to the piston coupling boss, and a linking member for connecting and thus integrating the piston coupling boss and the plurality of magnets. The linking member is formed of an injection molded resin, and the piston coupling boss and the magnets are coupled to the linking member at the same time that the linking member is injection molded.
Each of the magnets has a stepped portion that is formed along a boundary thereof.
The above object is also accomplished by a method for manufacturing a piston operating assembly for a linear compressor. The method includes the steps of preparing a plurality of magnets and a piston coupling boss, assembling the plurality of magnets and the piston coupling boss in a core mold, and mounting the core mold in an injection molding machine. The method further includes injecting a molding resin into the core mold to form an integrated piston operating assembly, with the plurality of magnets and the piston coupling boss fixed in the molding resin. The completed integrated piston operating assembly is then separated from the core mold, once the injection molding is finished.
Accordingly, the piston operating assembly of the linear compressor has improved geometric and assembling tolerances and persistence. In addition, the method of manufacturing such piston operating assembly is greatly simplified and results in an increase in productivity.